1. Field of the Invention
This invention relates to structures and methods for fabricating thin film magnetic write heads. More specifically, the invention relates to structures and methods for fabricating a thin film write head for perpendicular recording having independent control of track width, flare point, and a wrap around shield throat height which is self aligned to the flare point of the write pole. The methods and structure also provide for stepped wrap around shields wherein the thickness or depth (from the ABS) of the wrap around shield increases in the region above the write pole.
2. Description of the Related Art
As areal densities for magnetic storage hard disk drives continue to increase, the critical dimensions for thin film write heads are driven to smaller levels. For future designs, track widths (TW), flare points (FP), and wrap around shield throat heights (TH) will be on the order of 60 nm. Holding these dimensions provides a significant challenge for conventional processing, as will be illustrated in FIG. 1. FIG. 1 (Prior Art) is a partial plan view 100 of a typical thin film perpendicular write pole 212. Write pole 212 is typically imbedded in oxide layer 112, and is deposited after imaging the shape of the pole and etching oxide layer 112. Alternatively, write pole layer 212 can be blanket deposited, then imaged to define the final shape, etched or ion milled to define the pole, with areas around the pole subsequently filled with an oxide layer and both layers planarized. In either case, current imaging and etching processes can create errors with respect to the location of the flare point 102, since the position where the flare point is located by lithography FPd ref 104 will not be the actual location of the flare point FPa ref 106 subsequent to etching/milling of the pole material 212, or oxide layer within which the pole material is deposited. Errors can also be introduced with respect to the track width TW. The imaged track width TWd ref 108 may be larger or smaller than the actual value TWa ref 110. These errors also impact the location of the flare point. As dimensions are reduced, the location errors of the flare point can significantly impact the performance of the write head. Similar errors are introduced when locating and etching the cavities for the wrap around shield. The throat height, or the depth or thickness of the wrap around shield from the ABS, is critical to the performance of the write head. More particularly, the location of the rear of the wrap around shield relative to the flare point is critical, and is subject to significant errors when conventional lithography and etching processes are utilized to fabricate the shield. What is needed is a better process for producing perpendicular thin film write heads.
FIG. 2 (Prior Art) is a partial, cross sectional view of a typical thin film perpendicular write head 200. The head comprises shield layers 202, 204, shaping layer 210, coil structure 208, main pole 212, lower return pole layer 206, wrap around shield 214, and upper return pole layer 216. Alternatively, structure 214 may also be a trailing shield. Main pole 212 is typically deposited over spacer layer 112. Details of wrap around shields and trailing shields, as applied to perpendicular recording heads, can be found in, for example, US Patent Application Publications 2007/0146930, 2007/0115584, 2006/0174474, 2006/0044682, and 2007/0137027.